From: Paulo Marques <pmarques@grupopie.com>
To: Xiaofan Chen <xiaofanc@gmail.com>
Cc: mgross <640e9920@gmail.com>,
Alan Stern <stern@rowland.harvard.edu>,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [RFC] libusb / in-kernel usb driver criteria (was: USB driver for talking to the Microchip PIC18 boot loader)
Date: Wed, 02 Jan 2008 19:59:15 +0000 [thread overview]
Message-ID: <477BED13.4060403@grupopie.com> (raw)
In-Reply-To: <a276da400712292052h5808c33apd5269e773edfb592@mail.gmail.com>
Xiaofan Chen wrote:
> On Dec 30, 2007 11:53 AM, mgross <640e9920@gmail.com> wrote:
>> [...]
>> What is the linux-usb policies on new drivers that could be
>> implemented in user space? When does a kernel driver make sense over
>> a libusb one?
>
> That would be interesting to know.
I myself have been faced with this question before, and I think we
should try to clarify this by adding a document with some guidelines to
Documentation/usb.
So, to get the ball rolling, here are some factors that IMHO help decide
in which side to implement a driver:
- if the driver ties a hardware device to an existing in-kernel
interface (network, block, serial, bluetooth, video4linux, etc.), it
should probably be implemented in-kernel.
- on the other hand, if the driver doesn't use an existing kernel
interface and creates a new user-visible interface that is going to be
used by a single userspace application, it should probably be done in
userspace.
- if it is going to be used by several applications it could still be
implemented as a library, but it starts moving into the gray area.
- performance might be a reason to move to kernel space, but I don't
think it matters for transfer rates below 10Mbytes/sec or so.
Anyway, this is just MHO, so feel free to discuss this further. I'm
simply volunteering to sum up this thread into a patch to add a
Documentation/usb/userspace_drivers.txt (or something like that), so
that we can help future developers decide where to write their drivers.
--
Paulo Marques - www.grupopie.com
"Very funny Scotty. Now beam up my clothes."
next prev parent reply other threads:[~2008-01-02 19:59 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-29 19:34 [RFC] USB driver for talking to the Microchip PIC18 boot loader mgross
2007-12-29 22:15 ` Alan Stern
2007-12-30 2:40 ` Xiaofan Chen
2007-12-30 4:29 ` mgross
2007-12-30 4:46 ` Xiaofan Chen
2007-12-31 1:15 ` Xiaofan Chen
2007-12-30 3:53 ` mgross
2007-12-30 4:52 ` Xiaofan Chen
2008-01-02 19:59 ` Paulo Marques [this message]
2008-01-03 23:08 ` [RFC] libusb / in-kernel usb driver criteria (was: USB driver for talking to the Microchip PIC18 boot loader) mgross
2008-01-11 17:10 ` [RFC] libusb / in-kernel usb driver criteria Greg KH
2008-01-11 21:38 ` David Brownell
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